1. Field of the Invention
This invention relates to a wide band co-planar waveguide circularly polarized antenna capable of operating as a two-way radiation unit without a ground plate, or as a one-way radiation unit with a ground plate. As the antenna is being operated as a one-way radiation unit, the distance between the ground plate and the antenna body thereof can be reduced to 0.125 times of the wavelength of the signal transmitted or received by the antenna, which is smaller than the distance between the ground plate and the antenna body of a conventional antenna (which is 0.25 times of the wavelength of the signal transmitted or received by the conventional antenna). Therefore, while the wide band co-planar waveguide circularly polarized antenna of the present invention operates at a millimeter frequency band and as a one-way radiation unit, the size of the antenna can be further reduced so as to be packaged on a printed circuit board, along with a signal processor.
2. Description of Related Art
FIG. 1A is a schematic view illustrating the conventional wide band hole antenna, which comprises a substrate 11, an electric conductive plate 12, and a ground plate 13. The electric conductive plate 12 is located at one side of the substrate 11 and keeps a predetermined distance from the substrate 11. The ground plate 13 is located at the other side of the substrate 11 opposing the electric conductive plate 12 and integrates with the substrate 11. Further, the electric conductive plate 12 has a hole 121, and a feeding wire 14 sends a signal to the upper surface 122 of the electric conductive plate 12 surrounding the hole 121. FIG. 1B is a cross-section view of the conventional wide band hole antenna, along the I-I′ line in FIG. 1A. As shown in the figure, the substrate 11 comprises a plurality of electric conductive portions 112 located on the upper surface 111 of the substrate 11, and the ground plate 13 integrates with the lower surface 113 of the substrate 11. Moreover, each of the aforementioned electric conductive portions 112 is respectively electrically connected with one conductive portion 114, for electrical connection with the ground plate 13.
On the other hand, although the predetermined distance, labeled as D, can be smaller than one-quarter of the wavelength of the signal transmitted or received by the conventional wide band hole antenna, a plurality of electric conductive portions 112 having complex structures and a plurality of conductive portions 114 are required to be added into the conventional wide band hole antenna. Other than the rectangular-shaped hole 121 shown in FIG. 1A, the electric conductive plate 12 of the conventional hole antenna can have holes of any kind of shape, such as spindle-shaped or dumbbell-shaped, etc, which are shown through FIG. 2A to FIG. 2E However, no matter what kind of shape in which the hole is formed on the electric conductive plate, the conventional hole antenna can only transmit or receive a linearly polarized signal.
Therefore, the thickness of the conventional hole antenna cannot be further reduced, resulting in limited application field of the conventional hole antenna. Further, a circularly polarized signal is widely used in the communications application field, in order to prevent the downgrade of the efficiency of the transmission or reception of the high frequency signal by the orientation of the antenna. Therefore, the conventional wide band hole antenna which can only transmit or receive a linearly polarized signal is no longer capable of being considered in the future radio frequency communications application.
As a result, a wide band co-planar waveguide circularly polarized antenna having a reduced thickness and being capable of being packaged into a printed circuit board along with a signal processor is required in the radio frequency communications industry.